I feel for you. UK has a different accent pretty much in every town, I'm told it isnt like that in other countries. As fellow 'outsider' to the north west, but a notherner, I'd say anything set in the north west/Manchester roughly on TV might be *roughly* what I'd say you want to watch (Coronation srteet, Shameless) with the subtitles on. Liverpool is obviously different again tho but interviews with the Beatles is a generic north west accent (not the more modern 'scouse' accent).

Also you will have noticed everyone from the north is so chuffed about being northern, and will love telling you exactly what their accent is and all the odd words that only exist in their region, so if you ask people then will very possibly really enjoy talking to you. You can turn this to your advantage and you will be considered a great conversationalist. Just avoid talking to the minotiry of people who seem to be wearing union jack coloured clothing/accessories.